Effects of Exogenous Salicylic Acid on Morphological and Biochemical Characteristics of Jatropha Curcas L. Irrigated with Saline Water

Salinity is one of the major rate-limiting to crop productivity. A field study was conducted at two developmental stages of Jatropha curcas L. namely: the juvenile stage (1-2 years) and the early mature stage (3-4 years). Three levels of water salinity were prepared by diluting sea water (Suez Canal water) to give 2.3, 4.7 and 7.0 dSm^-1, in addition to fresh water (0.32dSm^-1). Jatrophaplants were foliar sprayed with three levels of salicylic acid (0.0, 5.0 and 10 mM). On thejuvenile stage, the obtained results indicated that the most effective treatment for vegetative growth characters such as total leaf area (TLA); leaf relative water content (RWC_L); relative growth rate (RGR) and leaf dry weight (LDW) was performed when Jatropha plants  were irrigated with fresh water, without significant difference, than that irrigated plants with either 2.3 or 4.7 dSm^-1. Application of 5.0 mM salicylic acid (SA) increased RGR, TLA and LDW for plants irrigated with saline water at 4.7 dSm^-1 as compared to either 0.0 mM or 10 m M SA.
On the early mature stage, application of 5.0 mM SA had a positive effect on both vegetative characters and seed yield for 4.7dSm^-1 salinity treatments as compared to control treatment. On the other hand, values of RWC_L indicated that there was no water deficit in leaves of treatments irrigated with saline water or control. This indicates that application of SAmay minimize salinity stress. Foliar application of SA effectively increased chlorophyll. Generally, spraying jatropha shrubs with SA had a positive effect in reducing the negative impact of water salinity.